Database updated in a mobile communication system

ABSTRACT

In a telecommunications system a data function and a date control function are replicated in a plurality of databases ( 50, 51, 52, 53, 54 ). In order to synchronize updating of the databases ( 50, 51, 52, 53, 54 ), one database is identified as a primary database ( 50 ), at least one is identified as a primary standby database ( 51 ), and the others identified as secondary databases ( 52, 53, 54 ). Then, in normal operation, the data control function of the primary database ( 50 ) is arranged to generate signals for synchronized updating of the other databases. In the event of a failure of the primary database, the or a standby primary database ( 51 ) takes over the up-grading operating. Tee present invention is particularly, but not exclusively, directed to a telecommunications system for mobile telephones.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a telecommunication system. The presentinvention is particularly, but not exclusively, concerned with atelecommunications system for mobile telephones.

SUMMARY OF THE PRIOR ART

When a telecommunication system involves mobile telephones, a call to amobile telephone is not to a fixed point, and therefore the system mustdetermine the location of the destination. The simplest arrangement isfor a call to a mobile telephone to result in a signal being transmittedto a data storage unit in the form of a Home Location Register unit(HLR) which determines the location of the mobile telephone, and sopermits routing of the call to occur.

Inevitably, HLRs have a limited capacity, and some arrangement istherefore necessary to enable telecommunication systems to accessmultiple HLRs. It should be noted that it is also envisaged that usersmay need multiple MSISDN numbers, for example if a user is to have thepossibility of both voice and data communication, in existing systems,any second MSISDN number with a common identity number (IMSI) must be aMSISDN number of the same HLR as the previous MSISDN number. This couldbe impossible to achieve if, for example, the HLR containing theoriginal information is full. Then the only way that additional servicescould be provided would require the user to change telephone number,which would be undesirable. This becomes a particular problem if it isdesirable that users are able to select their numbers, rather than beprovided with them.

WO 96/11557 (corresponding to U.S. Ser. No. 08/809,767) the disclosureof which is herein incorporated by reference, proposed that the switchnetwork which connects users to other users, HLRs, and system services,had a register unit associated therewith, which register unit containedinformation relating each telephone number to a corresponding one of aplurality of HLRs. The relationship between telephone numbers and HLRsshould then be freely selectable within the register unit, so that theregister unit acted as a converter between the number and theinformation identifying the HLR.

By providing such a register unit, the fixed relationship betweennumbers and HLRs was broken, and any number can be assigned to any HLR,assuming space permits. WO 96/11557 also proposed that the register unitstored further information associated with the mobile telephones whichpermits the switch network to enable calls from mobile telephones to berouted to different services, depending on the calling mobile telephoneitself, in addition to the number dialled.

SUMMARY OF THE INVENTION

The present invention develops further the ideas proposed in WO 96/11557by considering the location within which information is stored in thenetwork. In WO 96/11557, the question of the location of the registerunit was not considered.

When considering data in the network, there are two things that need tobe taken into account. The first is the storage of the data itself, andthe second is data control, being the means of handling queries,updates, results in synchronisation messages and similar controls. Thearrangement described in WO 96/11557 can be considered to be of thistype in that the register needs to store data, and also needs to storecontrol information for acting on that data.

At first sight, both the data and the data control functions may belocated at a single site, and stored on a single physical device such asa server which responds to queries and updates. The information storedmay be considered to comprise a data function and a data controlfunction, with the data function representing sets of data relating torespective telephone numbers, telephone control operations, etc. Thedata function and data control function may be considered to form adatabase of functions.

However, if there is only a single database that operate in this way,the network is vulnerable to failure. Therefore, at its most general,the present invention proposes that the database of functions bereplicated a plurality of times. Each database comprises a data functionand a data control function. The replicated databases may physically belocated in a single location, or may be at a plurality of physicallyseparate locations. In either case, each replicated database may beconsidered to be a service data function with each such function being anotional site in the network. The sites of the functions are thusvirtual sites, rather than being necessarily physically separate.

Preferably, each service data function may be stored on a separatestorage device. That storage device may also store other informationneeded by the network, or may control only the service data function.However, from an operational point of view, the relationships betweenthe service data functions are more important than their physicallocations. Although the service data functions represent a distributeddatabase, that distributed database must form a logically singularentity, even when physically distributed. Otherwise, the network willnot operate correctly. Therefore, control must be applied across thedistributed database.

For example, when considering such a distributed set of functions, it isimportant for the data functions to be synchronised and the data controlfunctions to interwork to control the synchronisation. Thissynchronisation includes not only the need for the information about anyparticular telephone number to be the same at each function, but alsofor the facilities associated with that telephone number to the same ateach function. The present invention therefore relates to thesynchronisation of those functions.

It should be noted that although the present invention has beendeveloped in connection with the register unit of WO 96/11557, thepresent invention is not limited to the operation of that register unit,and relates to arrangements in any network in which functions aredistributed. Where the present invention is used in connection with theregister unit of WO 96/11557, the register unit may be embodied in anyof the distributed service data functions, or the actions of theregister unit may be distributed across more than one service datafunction.

In a telephone network, it is important that any updating of thefunctions is carried out in real-time, and in a synchronised way. It isnot acceptable for the network to be updated gradually, as happens inexisting computer database techniques.

The present invention therefore proposes that, in a network ofinterconnected functions each of which is to be synchronised, one ofthose functions is identified as a primary function, at least one otherfunction is identified as a primary standby function, with any remainingfunction(s) being considered secondary. Then, when updating is needed,the primary function synchronises all other functions by signalling tothem an update that it has received. Those other functions then signalto the primary function that they have acted on the update. The primaryfunction may then signal externally that the update has occurred, and atthe same time provide acknowledgement signals to the other functions.

In principle, only the primary function can do this. However, if for anyreason the primary function fails, the primary standby function takesover control of the updating operation.

There may be multiple primary standby functions, although in a mobiletelephone system other constraints may limit arrangements to a singleprimary standby function. All other functions are secondary, in thesense that they are incapable of taking over control of the updatingoperation without re-programming of the network.

In such a system, requests for updating are sent only to the primaryfunction, unless that has failed, in which case all update requests aresent to the primary standby function.

In such an arrangement, it is possible for a secondary function to failto carry out an update correctly. In such circumstances, the primaryfunction is aware of this because it does not receive an appropriateacknowledgement, and tone secondary function is then treated asunsynchronised. In the unsynchronised state, the primary function willnot attempt to update the secondary function. There may, however, bearrangements to permit an unsynchronised secondary function to resume asynchronised state, by causing the primary function to transmit to thatsecondary function all updates which have occurred since the secondaryfunction became unsynchronised. Therefore, it is preferable that theprimary, the primary standby, and/or the secondary function is arrangedto record when any secondary function becomes unsynchronised.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the present invention will now be described in detail,by way of example, with reference to the accompanying drawings, inwhich:

FIG. 1 is a schematic block diagram of a telecommunication systemdescribed in WO 96/11557.

FIG. 2 shows part of the telecommunication system of the presentinvention; and

FIG. 3 shows part of the arrangement of FIG. 2, in terms of significantfunctional components.

DETAILED DESCRIPTION

Referring first to FIG. 1, and as discussed in WO 96/11557, a switchednetwork 10 interconnects land-based and mobile telephones. If a call toa mobile telephone is made from a land-based telephone, the call isrouted via the public switched telephone network (PSTN) 11 to the switchnetwork, and from that switch network 10 to the mobile telephone (BSS)12. To do this, the switch network 10 must determine routinginformation, and to determine that routing information it must determinethe location of the mobile telephone 12, which it does via a HLR towhich the mobile telephone 12 is associated. When there are multipleHLRs 13,14, it is necessary for the switch network 10 to determine whichHLR 13,14 must be accessed, on the basis of the telephone number (MSISDNnumber) of the mobile telephone input by the originator of the call.

The switched network 10 accesses a register unit 15, which identifiesthe called number and addresses it to a particular HLR 13,14 with whichthe mobile telephone 12 is associated. The register unit 15 permits therelationship between any given mobile telephone number and the HLRs13,14 to be determined freely, so that the number is unaffected by theparticular HLR 13,14 with which it is associated. The register unit 15removes the need for a particular mobile telephone number to beassociated with a fixed HLR 13,14.

Once the particular HLR 13,14 with which the mobile telephone 12 isassociated has been identified, signalling can occur to that HLR, andinformation derivable therefrom, in the usual way. This information isused to “set-up” the call to the mobile telephone 12, which may then berouted to the destination telephone as is normal.

Similarly, if a call originates at the mobile telephone 12, the switchnetwork 10 must again determine the routing of that call. If the call isto a land-based telephone, connected to the switch network 10 via thePSTN 11, then this routing can be on the basis of the telephone numberof the destination telephone, in the normal way.

If a call is made from a mobile telephone 12 to one of a plurality ofvoice processing systems 16,17 or to services 18 associated with theswitch network using a short code (e.g. 123) the relationship betweenthe mobile telephone 12 and the corresponding service must be determinedby the register unit 15 before the switch network can determine theappropriate voice processing system 16,17 or services 18 to be accessed.

FIG. 2 shows the switch network 10 in more detail. It has a plurality ofmobile switching centres (MSC) 20,21 and 22, and a call destined to anygiven mobile telephone results in signalling between that MSC 20-22 andone of a plurality of signalling transfer points (STP) 30,31, whichsignal to the register unit 15 to determine the HLR 13,14 which isappropriate to the mobile telephone 12. The register unit 15 of FIG. 1derives that information from the telephone number (MSISDN number) ofthe mobile telephone 12. It would then be possible for the register unit15 to forward the signal directly to the appropriate HLR 13,14 but, itis preferable that the information is passed back to the correspondingSTP 30,31 which then passes the signalling to the correct HLR 13,14.

A similar signalling flow occurs when the user of the mobile telephone12 tries to access a voice processing system (VPS) 16 or a service node(SN) 17. The call is received by one of the MSCs 20,21 and 22 whichpasses the dialled digits and the identity of the mobile telephone toone of the STPs 30,31,32. This relays the information to the registerunit 15, which uses this information to construct the correct address ofthe appropriate voice processing service (VPS) 16 or service node (SN)17. That information is relayed back from the register unit via one ofthe STPs 30,31,32 to the original MSC 20,21,22. This address is thenused to route the call by the switch network 10. That routing passes thecall from the appropriate MSC 20,21,22 via the switch network to the VPS16 or the SN 17.

In the arrangement shown in FIG. 2, the register unit 15 is not a singlecomponent, but comprises a plurality of units hereinafter referred to asservice control points (SCP) 40. There are N SCP 40, wherein N is aninteger being 2 or greater. At least two SCP 40 are needed in order toprovide a replicated database for load sharing and fault tolerance.

In the arrangement of FIG. 2, the SCPs 40 are interconnected by a dataconnection 41, and the system also has a controller (NMS) 42 thatmonitors the service control points (SCP) 40.

FIG. 2 illustrates the arrangement of the network in structural terms.However, it is also possible to think of the arrangement in functionalterms, and the significant functions of the arrangement of FIG. 2 areillustrated in FIG. 3. The SCPs 40 may, collectively, be considered as aplurality of functions, primarily data functions, which collectivelyprovide a centralised repository for service/subscriber related data.Each of these functions will be referred to as a service data functionor SDF. Thus, as shown in FIG. 3, a plurality of such functions (SDFs)50,51,52,53 and 54 are interconnected, and connected to the dataconnection 41. FIG. 3 also shows a service control function SCF 55 whichis a logical element (in the same way as the SDFs 50-54 are logicalelements) corresponding to VPS 16, service node 19 etc. in FIG. 2. TheSCF 55 can be thought of as a “client” within the network which requestsdata from, updates to, etc the SDFs 50-54.

One of the SDFs 50 is designated a primary function, and has primaryresponsibility for synchronising updating of the other SDFs 51-54. Thelink between the SCF 55 and the data connection 41 is a path for databeing retrieved by an SCF 55, and also of update information to the SDF50.

At least one other SDF 51 is designated a primary standby function andhas a similar link 57 to the connection 41. As will be discussed in moredetail later, the primary standby function 51 operates to take over thecontrol of updating carried out by the primary function 50 if theprimary function 50 is unable to carry out that operation correctly.Whilst there may be more than one primary standby function, in thearrangement shown in FIG. 3, all the other SDFs 52,53,54 are secondaryfunctions. Those secondary functions 52,53,54 are also connected bysuitable connection 58, 59, 60 to the data connection 41. Thoseconnections 58, 59, 60 are involved in retrieval of data for an SCF,synchronisation of updates from the primary function SDFs, but notdirectly in updating from an SCF. Instead, all the SDFs 50-54 areinterconnected for updating controlled by the primary function 50, orthe primary standby function 51. In fact, those interconnecting arenormally via connections 56 to 60 and data connection 41, but forfunctional purposes may be considered to be direct as shown in FIG. 3.

In normal use, functions (SDFs) 50-54 provide a composite memory inwhich, in a mobile telephone system, information about users, networkfunctions, etc may be stored as discussed in more detail in WO 96/11557.

The present invention, however, is particularly concerned with theupdating of the function network thus created.

In normal operation, a request for updating of data stored in the SDFs50-54 is received at the primary function 50. When update information isreceived by the primary function 50, the primary function 50 signals theupdate to all other functions 51-54. When those functions 51-54 haverecorded the update, they signal back to the primary function 50 thatthe update has been completed. Thus, the primary function 50 can storeinformation confirming that all the other functions 51-54 have beensuccessfully updated. The primary function 50 may then signal to the SCF55 to confirm that the update operation has been completed, and alsoconfirm to the other functions 51-54 that it has recorded the completionof the update and that the SCF has been notified. Thus, at all times,the functions 50-54 are synchronised.

If any secondary function 50-54 fails successfully to record an update,this will be detected by the primary function 50 and that secondaryfunction will then be considered unsynchronised, and thus not a reliablesource for data. The primary function 50 will not attempt to sendfurther update signals to such an unsynchronised secondary function. Ofcourse, if there are too many failures, the primary function maydetermine that the attempted update of the network of functions haswholly failed, in which case a suitable signal will be sent to the SCF55, and the update operation rejected.

It is preferable that an unsynchronised secondary function cansubsequently return itself to the synchronised state. An unsynchronisedsecondary function may signal to the primary function 50 an indicationof the last update which it successfully completed. The primary function50 may then determine all subsequent updates and transmit all thoseupdates to the unsynchronised secondary function. If the unsynchronisedsecondary function successfully records all those updates, it may beconsidered to have returned to synchronisation. Once synchronised, theprimary function 50 will continue to update that secondary function inthe normal way.

Under some circumstances, the primary function 50 may need to be closeddown. For example, this may be because the hardware on which the primaryfunction 50 is resident needs to be maintained. To prevent the networkof functions having to be closed down at this time, the actions of theprimary function 50 are transferred to the primary standby function 51.This hand-over of operations is signalled between the primary function50 and the primary standby function 51, and also with the SCF 55. Anyexisting updates should be completed before this hand-over occurs, sothat all SDFs are synchronised prior to the primary standby function 51taking over.

This procedure can also apply in an unexpected failure of the primaryfunction 50. As has previously been mentioned, when the primary function50 has received confirmation from all the other functions 51-54 thatupdating had occurred, it notifies the requesting SCF and then signalsan acknowledgement to those other functions. If that acknowledgement isnot received by the primary standby function 51 within a predeterminedtime and the primary standby function 51 is informed by the switchednetwork 10 that the primary function is unavailable, the system may bearranged so that the primary standby function 51 then automaticallytakes over control of the network functions 50-54 under the assumptionthat the primary function is no longer available.

Simultaneous failure of one or more secondary functions does not preventthe network of functions operating successfully, and either the primaryfunction 50 or the primary standby function 51 may fail, in combinationwith any of the secondary functions 52-54 and data updating and queryingwill still be possible. However, if both the primary function 50 and theprimary standby function 51 fail at the same time, then the remainingnetwork of functions will only be able to support data retrievals; dataupdating will not longer be possible. For this reason, it may bepreferable to provide multiple primary standby functions, although otherconstraints within mobile telephone networks may prevent this.

It should be noted that although FIG. 3 illustrates an embodiment withfive functions (SDFs) 50-54, the minimum number of functions to achievethe present invention is two. In such an arrangement, one function actsas a primary function, and the other acts as a primary stand-byfunction. Further secondary functions then increase redundancy and loadsharing.

In the above description, each service control point (SCP) 40 wasassociated with a corresponding SDF 50 to 54. It should be noted thatany single SCP 40 may act as the storage site for only the correspondingSDF 50-54, or may store other information, such as data or controloperations.

Moreover, in the preceding description, the present invention has beendescribed in terms of a way of implementing the arrangements discussedin WO 96/11557. However, the present invention is not limited to this.The operations carried out by the SDF 50-54 may be any data and/or datacontrol functions. The operations described with reference to WO96/11557 then act as examples of such functions.

1. A telecommunication network having at least one database of functionsfor controlling the network, said database comprising at least a datafunction and a data control function; characterised in that: thedatabase is replicated a plurality of times, the database of one of saidreplicated databases is a primary database, the data control function ofwhich is arranged to generate signals for synchronised updating of allof said replicated databases, at least a second database is a primarystandby database, the data control function of which is arranged togenerate signals for synchronised updating of all of said replicateddatabases in the event of a failure of said primary database, and atleast one secondary database other than said primary database and saidprimary standby database, wherein the at least secondary database isarranged to signal to said primary and/or said primary standby databasewhen it has been updated in response to the updating signals from saidprimary database or said primary standby database.
 2. A networkaccording to claim 1, wherein a plurality of databases are primarystandby databases.
 3. A network according to claim 1, wherein the atleast one secondary database is a plurality of secondary databases.
 4. Amethod of operating a telecommunication network, in which the network iscontrolled by at least one database of functions, said databasecomprising at least a data function and a data control function;characterised in that: the database is replicated a plurality of times,and the method comprises: designating one of said replicated databasesas a primary database; designating at least one other of said replicateddatabases as a primary standby database; designating at least one otherof said replicated databases as a secondary database; updating all ofsaid replicated databases on the basis of updating signals from saidprimary database unless said primary database has failed; updating allof said replicated databases on the basis of updating signals from saidat least one primary standby database when said primary database hasfailed; and signaling to the primary and/or the primary standbydatabase(s) when the at least one secondary database has been updated inresponse to the updating signals from the primary database or theprimary standby database.
 5. A method of operating a telecommunicationnetwork according to claim 4, wherein the at least one secondarydatabase is a plurality of secondary databases.
 6. A telecommunicationsnetwork comprising: a primary database having at least a data functionand a data control function; and a plurality of databases which arereplicas of the primary database, wherein at least one of the pluralityof databases in a primary standby database, and wherein at least oneother of the plurality of databases is a secondary database; wherein thedata control function of the primary database is arranged to generatesignals for synchronised updating the plurality of databases, andwherein the data control function of the primary standby database isarranged to generate signals for synchronised updating of the pluralityof databases in the even of a failure of the primary database; andwherein the at least one secondary database is arranged to signal to theprimary or the primary standby database when it has been updated inresponse to the updating signals from the primary database.
 7. A networkaccording to claim 6, further comprising a plurality of primary standbydatabases.
 8. A telecommunications network according to claim 6, whereinthe at least one secondary database is a plurality of secondarydatabases.
 9. A method of operating a telecommunication network,comprising: providing an initial database having at least a datafunction and a data control function; replicating the initial databaseto form plurality of replicated databases; designating one of thereplicated databases as a primary database; designating at least oneother of the replicated databases as a primary standby database;designating at least one other of said replicated databases as asecondary database; updating all of the replicated database on the basisof updating signals received from the primary database unless theprimary database has failed; updating all of the replicated databases onthe basis of updating signals from the at least one primary standbydatabase when the primary database has failed; and signaling to theprimary and/or the primary standby database(s) when the at least onesecondary database has been updated in response to the updating signalsfrom the primary database or the primary standby database.
 10. A methodof operating a telecommunication network according to claim 9, whereinthe at least one secondary database is a plurality of secondarydatabases.